Trauma Protocol: Hemorrhagic shock is a dominant cause of death after trauma. The detrimental effects of assisted positive pressure ventilation (PPV) on cardiac output in hypovolemic patients has been under-appreciated. PPV has not been recognized as a negative confounding variable in outcome. Recent studies of severe hemorrhage show that perfusion and survival are significantly improved with lower ventilatory rates. Ironically, emergency care personnel are still being trained to use high rates of PPV in hypotensive trauma patients. Our central hypothesis: assisted ventilation rates commonly used in the pre.hospital setting adversely affect mortality and neurological outcome in patients with post-traumatic hypotension and that using a lower ventilation rate such as 6 breaths per minute will improve outcome significantly. Specific Aims: To establish that survival and neurological outcome are significantly improved in cases of post-traumatic hypotension when emergency care providers deliver controlled rates of PPV as compared with the current practice of uncontrolled rates of PPV. In addition, further improvements are gained using controlled ventilation rates of 6/minute compared with 12/minute. Cardiac arrest protocol: Even when receiving standard, manual CPR techniques, most patients who have out-of-hospital cardiac arrest still die prior to arriving at a hospital. Many factors contribute to these poor survival statistics, including the inefficiency of the CPR technique itself. CPR provides only 10% to 20% of normal myocardial perfusion, and only 20% to 30% of physiologically normal cerebral perfusion even when performed early. In this proposal, we have selected what we believe is the most promising approach to improving CPR efficiency, patient survival, and neurological outcome following cardiac arrest. This approach is the combination of active compression-decompression (ACD) CPR and the impedance threshold device (ITD), a technique termed ACD+ITD CPR, which enhances vital organ perfusion during the decompression phase of CPR. Specific aim: To determine whether ACD+ITD CPR will improve survival to hospital discharge and neurological outcome after witnessed, out-of-hospital cardiac arrest in adults (primary endpoint) when compared with standard closed chest CPR.